Re: Sorting through old screw bins. How to tell silicon bronze from brass?
In the do as I say not as I do department, you might try the vinegar test:
The old Lydian stone trick comes to mind, but you will need to see if the color difference is good enough to tell.
The lydian stone is hard, black and acid resistant, so it works by giving a good color contrast and survives a lot of testing without regrinding the surface.
Lydian is basinite is similar to novaculite. Black novaculite is a good grade of Arkansas stone, so if you want to pay more than the screws are worth to try a scratch test on something more durable than 600 grit wet or dry paper, the stone will be a good addition to your sharpening tool kit. http://www.naturalwhetstone.com/productssharpening2.htm
I would toss the screws in a plastic colander and pour some muriatic acid or Tarn-x over them hoping to get a discernible color difference.
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